In the background art, when cutting such as turning or milling is performed on a workpiece such as a steel material by using a cutting tool such as an end mill or a milling cutter, cutting has been performed after “cutting conditions” such as a feed speed of the cutting tool, a cutting amount by the cutting tool, a cutting speed of the cutting tool, the shape of the cutting tool, etc. are made appropriate.
When cutting is performed by using an end mill or a milling cutter, a chattering vibration may occur during the cutting depending on the shape of a cutting tool, or the shape of the cutting tool may be deformed. When such a chattering vibration occurs, there occurs a severe problem as to the machining accuracy or the machined surface property of a workpiece. Therefore, an operator who designs the cutting conditions for the cutting should set the “cutting conditions” to reduce the feed speed of or the cutting amount by the cutting tool to thereby reduce a load in order to prevent the aforementioned problem from occurring.
In addition, as to the tool life of a cutting tool, there arises such a problem that the tool life becomes extremely short when cutting is not performed under appropriate cutting conditions. However, it is difficult to accurately find the cutting conditions with which the tool life can be elongated, and therefore cutting conditions (particularly the cutting speed of the cutting tool) is designed with a margin in many cases.
However, the cutting conditions thus provided with a margin may lead to an excess cost for cutting. For example, there is a problem that a cutting tool may be replaced before reaching its tool life, or cutting time may be increased due to the low-load cutting conditions.
In order to improve such situation, techniques for designing optimum cutting conditions have been developed. The techniques for designing optimum cutting conditions are, for example, ones as disclosed in Non-Patent Literature 1 and Non-Patent Literature 2.
According to Non-Patent Literature 1, in an off-line manner, the shape of a workpiece having been subjected to cutting is measured, and cutting conditions are optimized based on the measured value and an instruction value given in advance for the cutting. Next, in an online manner, a tool life test is performed on a cutting tool, and the tool life and the machining efficiency are converted into losses by a loss function and evaluated on the same dimension. Then, appropriate cutting conditions are designed from the relationship between the tool life and the machining efficiency.
According to Non-Patent Literature 2, a formulation for optimizing cutting conditions in cutting is established by nonlinear goal programming, and appropriate cutting conditions are designed based on the formulation.